178 
GEOLOGY. 
clay. They may be traced running in broken lines nearly east and west, or a little on 
the south side of east and north of west. 
The coral reefs along the coast are of two sorts ; one above low water mark, and in 
which the animals are dead, is dark, cellular, and rough, similar to what generally forms 
the rocky inland eminences ; the other is always covered by the sea, and generally pre- 
sents an arborescent surface of brown or white colour, and is at this time occupied by the 
living animals. But even these have a darker appearance than is usual in growing corals 
among the islands nearer the equator, apparently from a quantity of mud and clay depo- 
sited among' the crevices, and which seems to be continually supplied from the soil and 
the marly detritus of the island, washed down by rains and rivulets; for I saw nothing 
that was entitled to the name of a river, unless we may dignify with that appellation a 
moderately-sized stream that comes down from the principal lime-stone ridge, a little to 
the west of the village of Xslioomee, and of the building called Eepang-kwang. 
The soil of the island in the vicinity of Nawha is in general light, arenaceous, and 
marly. In a few places only does it approach to clay, and rarely is it of any considerable 
depth. The rivulets are few in number ; and I observed no moist plains or marshes, ex- 
cepting a very few fields in which the water is retained by artificial means, chiefly among 
the blue marly eminences to the south-east of Abbey Point, already mentioned. 
The plants which grow wild are made up of the floras of the torrid and temperate 
regions ; we have ferns and palms, compound and umbelliferous plants ; and the boer- 
liaavia, scoevola, tournefortia, &c., growing in similar situations as in the low islands of 
Polynesia. Several rosaceae, onagreee, prunulaceae, &c. associate the vegetation of 
Loo Choo with that of the temperate continents of Asia, and even of Europe. The re- 
markable genus clerodendron is perhaps peculiarly abuudant here. 
ISLANDS OF THE ARZOBISPO GROUP, 
OF WHICH THE LARGEST IS PEEL ISLAND, 
From lat. 26° 30' to 27° 45' N, ; long. 217° 48' W. 
The Arzobispo Group, or Bonin Islands, are considerable, if we regard their num- 
ber alone ; we saw five groups, each composed of several islets. If we take into ac- 
count, however, the superficial extent of land, and still more of productive soil, they 
will be lessened in our estimation. They seem to be universally volcanic, if I may judge 
of the similarity of those I saw at a distance to those which I had an opportunity of ex- 
amining, excepting some bare and bordering rocks of coral, raised most probably above 
the level of the sea by subterranean power. The hills are peaked, the shores precipi- 
tous, with deep water close to them ; but pointed pinnacles rise up from the bottom 
nearly to the surface for some distance, and endanger the navigation. 
The mountain ridges, as well as the groups of islands, lie in a north and south di- 
rection, and appear to be only the more elevated tops of a subaqueous chain extending 
in the same direction ; for in sounding we always found it shallower on a line connect- 
ing the groups from north to south, than at the same distance from the shore on either 
side of this line. 
